1. Field of the Invention
This invention relates generally to a pollution control system and, more particularly, this invention relates to a method of removing condensable pollutant materials from a high-temperature gas stream.
2. Brief Description of the Prior Art
Pollution control processes utilizing counterflow of a liquid absorbent with a liquid or solid pollutant-laden gas stream to remove pollutants from the gas stream are well known. Further, pollution control processes utilizing electrostatic precipitators or equivalent means to separate particulate materials from gas streams are well known.
However, the inventors have discovered that, under certain circumstances, the application of counterflow gas-liquid contact pollution control procedures results in serious problems. Specifically, when the temperature difference between a polluted gas stream and a liquid absorbent stream is relatively high, certain types of condensable pollutants in the gas form a non-absorbable fog or mist. Under such circumstances, the fog cannot readily be eliminated by control of column height or absorbent or gas flow rate.
The inventors have discovered that cool counterflowing liquid absorbent causes such extremely rapid condensation of the vaporized material that formation of a fine fog of such material occurs, and that the fog is carried from the counterflow packed bed regardless of other process variables.
Further, both heat exchanger cooling surfaces and electrostatic precipitators or filters used in prior pollution control processes have exhibited a tendency to become fouled after only short periods of use.
Counterflow liquid-gas contact processes have not been successfully applied to the reduction or removal of pollutants from discharge streams of heatset printing press dryers. In prior practice, pollutants have been removed from such streams by means of afterburners, which operate at high temperatures and which burn natural gas or a similar fuel. The energy requirements of such burners are high.